Rearview mirrors are essential for the safe operation of motor vehicles. Ordinary flat rearview mirrors are known to have a "blind spot" which is located adjacent the vehicle and to the rear of the driver. The "blind spots" frequently lead to accidents particularly when the driver changes lanes.
An obvious solution to the "blind spot" problem is to have the rearview mirror outside the car adjusted to capture the "blind spot" area. To compensate for the missing field of view in the outside mirror, one may adjust the mirror inside the car. This requires the outside rearview mirror to be angled such that none of the driver's car is in the field of view. Since the view through the outside mirror when in that position does not show the relationship of the driver's car to the field of view, few drivers employ this method. Most drivers place the outside mirror at an angle which encompasses the side or rear of his or her car.
There have been many other attempts to solve the "blind spot" problem. Truck drivers, for example, use a mirrored hemisphere placed on the rearview mirror with the hemisphere's convex side exposed. Because trucks normally have large mirrors, the mirrored hemisphere solution often suffices. This method, however, should not be used on cars with conventional rearview mirrors because the hemisphere is aesthetically displeasing, distracting, and takes up too much of the total area of the flat section of the mirror so that it is unable to properly function.
Much work has been done in this field, and relevant patents of which the applicant is aware are U.S. Pat. Nos. 3,175,463 issued Mar. 30, 1965, 3,389,952 issued June 25, 1968, and 4,306,770 issued Dec. 22, 1981, German Patent No. 2,213,586 issued Oct. 4, 1973, and European Patent No. 210,757 published Feb. 4, 1987. Of these the European patent is the most relevant. However, the rearview mirror of that patent includes a slopinq section between and joining a flat section to a convex area of changing curvature. The convex area of changing curvature creates continual distortion as the object is viewed in the mirror moves away from the flat section further into the convex area. The patent indirectly mentions that a convex section with a constant rate of curvature can be used, but the sloping section remains. The reason that the device of the European patent produces too much distortion in the area of constant rate of convexity is because of the gradual slope leading into the convex area. Elimination of this slopinq area is very important since any sloping creates distortion in the form of narrowing and shrinking objects.